# US 5,702,668 A · Cobalt-free hardfacing alloys with improved welding characteristics

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- Number: US 5,702,668 A
- Document ID: US5702668A
- Status: Granted
- Kind: A
- Application number: 08/708,177
- Filed: 1996-09-06
- Granted: 1997-12-30
- Earliest claimed: 1994-11-03
- Assignees: Electric Power Research Insitute, Inc.
- Inventors: Howard Ocken; Shane J. Findlan; Michael K. Phillips
- Web page: https://patentgrep.com/patent/US5702668A

## CPC

- C22C 38/58: with more than 1.5% by weight of manganese
- B23K 35/3086: {containing Ni or Mn}
- B23K 9/04: Welding for other purposes than joining, e.g. built-up welding
- C21D 2211/001: Austenite
- C21D 2211/003: Cementite
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)

## Abstract

Novel cobalt-free iron-base, wear-resistant and anti-galling, hardfacing alloys are provided. These alloys are capable of being deposited on substrates by welding without preheating the substrate, thus facilitating field applications of cobalt-free alloys.

## Claims

### Claim 1

A cobalt-free iron-base wear-resistant and anti-galling hardfacing alloy consisting essentially by weight of about 1.10-1.35% carbon; at least 4.0%, but less than 5.0% manganese; 3.0-3.5% silicon; 22.5-26.0% chromium; 3.7-4.2% nickel; 1.82.2% molybdenum; 0.02-0.18% nitrogen; less than 0.018% phosphorus; less than 0.010% sulphur; less than 0.002% boron; and the balance iron; said alloy having a microstructure consisting essentially of austenitic matrix and eutectic alloy carbides.

### Claim 2 (depends on 1)

An alloy according to claim 1 wherein said silicon is present in about 3.1-3.5%; chromium is present in about 24.0-26.0% and nitrogen is present in about 0.14-0.18%.

### Claim 3 (depends on 1)

A alloy according to claim 1, wherein said alloy is capable of being deposited on a substrate by welding, wherein preheating of the substrate is unnecessary.

### Claim 4 (depends on 1)

An alloy according to claim 1, consisting essentially by weight of 1.25% carbon; 4.5% manganese; 3.3% silicon; 25.0% chromium; 4.0% nickel; 2.0% molybdenum; 0.16% nitrogen; less than 0.018% phosphorus; less than 0.010% sulphur; less than 0.002% boron; and the balance iron; said alloy having a microstructure consisting essentially of austenitic matrix and eutectic alloy carbides.

### Claim 5

In a method for constructing a plant comprising elements exposed to an aggressive environment, the improvement comprising the step of forming said elements from a cobalt-free iron-base wear-resistant and anti-galling hardfacing alloy consisting essentially by weight of about 1.10-1.35% carbon; at least 4.0%, but less than 5.0% manganese; 3.0-3.5% silicon; 22.5-26.0% chromium; 3.7-4.2% nickel; 1.8-2.2% molybdenum; 0.02-0.18% nitrogen; less than 0.018% phosphorus: less than 0.010% sulphur; less than 0.002% boron; and the balance iron; said alloy having a microstructure consisting essentially of austenitic matrix and eutectic alloy carbides.

### Claim 6 (depends on 5)

A method according to claim 5, wherein said alloy contains about 3.1-3.5% by weight silicon about 24.0-26.0% by weight chromium and about 0.14-0.18% by weight nitrogen.

### Claim 7 (depends on 5)

A method according to claim 5, wherein said alloy is capable of being deposited on a substrate by welding, wherein preheating of the substrate is unnecessary.

### Claim 8 (depends on 5)

A method according to claim 5, wherein said alloy consists essentially by weight of 1.25% carbon; 4.5% manganese; 3.3% silicon; 25.0% chromium; 4.0% nickel; 2.0% molybdenum; 0.16% nitrogen; less than 0.018% phosphorus; less than 0.010% sulphur; less than 0.002% boron; and the balance iron; said alloy having a microstructure consisting essentially of austenitic matrix and eutectic alloy carbides.

### Claim 9 (depends on 5)

A cobalt-free iron-base, wear-resistant and anti-galling, hardfacing structural element for use in an aggressive environment produced according to the method of claim 5.

### Claim 10 (depends on 3)

An alloy according to claim 3, wherein the substrate is carbon steel.

### Claim 11 (depends on 3)

An alloy according to claim 3, wherein the substrate is stainless steel.

### Claim 12 (depends on 3)

An alloy according to claim 3, wherein the welding is gas tungsten arc welding.

### Claim 13 (depends on 5)

An alloy according to claim 5, wherein said plant is a nuclear power plant.

### Claim 14 (depends on 1)

An alloy according to claim 1, wherein said alloy is cast.

### Claim 15 (depends on 1)

An alloy according to claim 1, wherein said alloy is in strip form.